Free Shipping on all orders $35 and up.

We offer standard delivery in 3 business days or less.

Please see our shipping map below for estimated times.

Estimated standard delivery time to the U.S. and Puerto Rico

Delivery time estimates do not apply to large or heavy items that require special
shipping (including most TVs), items shipped directly from the manufacturer, or
out-of-stock items. Some items that ship from the manufacturer can only be delivered
to addresses within the 48 contiguous states.

Delivery time for standard shipping to any of the 50 U.S. states or Puerto Rico is 1-3 business days. Saturday, Sunday and national holidays are not considered business days for delivery purposes.

Factory-authorized dealer

Headlights dim when the music plays

What to do to give your car's electrical system a power-up

Buck Pomerantz was born and raised in Philadelphia. His parents bought their first television set when he was born. He figured out how to run it by the time he was two. Besides athletics, his formative interests included electronics, amateur radio, music, and stage crew work. He got his BA in writing from Brown University. Then he joined a rock 'n roll band as their soundman and moved to Charlottesville, Virginia. After that venture failed, he spent time in Boston, New Orleans, and Berkeley. He worked in a music store in Austin manufacturing, installing, repairing, and operating sound systems for recording studios, clubs, and bands. He moved back to Charlottesville, ran a little recording studio and finally joined Crutchfield as a copywriter. He has 2 grown children and 3 grandchildren, but after a good nap he can still rock out.

Your headlights dim when the stereo pulls too much power out of your car's electrical system. This usually happens only in large, multiple-kilowatt sound systems. But sometimes even modestly powered systems can stress your car's electronics, especially during a sub amp's burst of energy when it produces the sound of the beat. Every part of the electrical system suffers because of the amp's sudden demand on the limited supply of power, even the amplifier itself. Your eyes are just more sensitive to the change than your ears, and you notice your headlights dimming along with the beat.

There are a few actions you can take to solve this problem. There are also some strong and differing opinions about the order in which you should do them, or even their individual usefulness. The following is my contribution to the argument.

Sometimes all you need is a new battery terminal.

Check all power and ground connections, and the battery itself

The first thing you should do is make sure all the surfaces used in power and ground connections are scraped down to bare metal, clean, and all the connectors and the battery terminals fastened tightly together. If that doesn't do it, take your car and have its battery load-tested at an auto parts or battery store. They'll often do it for free and can recommend the proper replacement if they find your old battery has problems. Car batteries rarely live to be four years old, so don't think you're being cheated when they tell you your old battery isn't holding its charge. A weak battery can often have enough juice to start your car but not be able to handle the quick jolt of demand when your sub amp hits.

If you do decide you need to replace your battery, consider getting an XS Power battery from Crutchfield. XS Power batteries feature a sealed absorbed glass mat (AGM) design, instead of the standard liquid electrolyte design, so they actually store energy — meaning you don't have to add a capacitor to your system to get a quick burst when you need it. We carry a full assortment of the most popular sizes available. We even have models which fit many European applications such as VW/Audi, BMW, Mercedes, and Jaguar.

T-Spec 3.0-Farad capacitor

Capacitors

Adding a capacitor to your system does not increase your system's power capacity. But if your lights dim only occasionally, and only on the loud drum beats, then a capacitor may just be the cure. A capacitor smoothes out the power demands by providing a short burst of energy when needed. I recommend 2 farads of capacitor for every 1,000 watts RMS of total amplifier power. That's more than the usual recommended dose, but it should ensure a quicker recovery time for the cap to be ready for the next thump.

The Big Three wiring upgrade

A good, cost-effective improvement is to perform the "Big Three" electrical upgrade. This will vastly improve your vehicle's electrical system, allowing more current to flow easier to all components. This upgrade replaces or augments three key cables in the electrical system with 1/0 or 4 gauge wires: the battery ground to chassis wire, the chassis to engine block wire, and the alternator plus to battery plus wire. This increases your electrical system's current flow capability, ensuring a more consistent voltage under varying demand conditions.

An unfortunate possible side effect of doing the Big Three is that occasionally it only makes your lights dim even worse. This happens because the amplifier is now able to suck juice better from the system through the bigger straw (the new cables).

High output alternator

The alternator is the ultimate source for all of your vehicle's power when it's running. The battery starts the engine, but the alternator takes over when the motor starts to turn. If your sound system demands more power than your stock alternator can supply, then you will benefit by upgrading to a higher output alternator. Replacing your stock alternator with an "HO alt" may seem like an expensive solution, but if you've invested in a sound system that draws this much power, you shouldn't mind solving this problem of supply and demand by increasing the supply of power.

For example: producing a 1500 watt output requires about 217 amperes of current from your car's system. It's actually about a third of that for music, which doesn't put out full power all the time — but it's still a lot of current. Most stock alternators are in the 80-120 ampere range and can only supply about 40% to 50% of that for non-automotive uses like amplifiers.

A 250 or 300 ampere aftermarket high output alternator should provide enough power for all your car's systems and your high-powered stereo too. Keeping that in mind, calculating the required output size of a high output alternator is not easy and should only be done while consulting with the new alternator's vendor or installer.

XS Power car batteries

Adding a second battery

Another method is to add a second battery, often back near the amplifier. This, in effect, provides another source of power available to fill in the gaps when the system needs it. When the power is asked for, it comes from the batteries. Two batteries wired in parallel act like one battery with twice the capacity. Crutchfield carries secondary battery wiring kits that feature all the hardware necessary for adding a second battery to your system.

A second battery becomes almost necessary if you play your music a lot with the engine turned off. Some people use isolators between their batteries, so that the one used to start the car won't get drained by the amp's pull. And it's a good idea to only hook up two batteries of equal strength and age. The stress of two different strength batteries constantly cycling charge between themselves to equalize the voltage leads to a shortened life for both batteries.

Note: Working with a car's electrical system can be dangerous. Tools and jewelry can be welded by the inadvertent discharge of a battery or capacitor. Sparks could fly, igniting flammable gases. Batteries have been known to explode when overstressed. (I know it for a fact: I witnessed a friend's battery exploding and setting his Lincoln on fire.) If you're inexperienced or don't feel comfortable working with high-current devices, then hire a professional to do these upgrades and installations.

And please, don't let anyone talk you into doing any of these procedures unless you are experiencing bothersome headlight dimming.

Comments

Daniel from Chicago

2 Quick questions: I have a 2014 Dodge Charger SXT. I plan to install one (1) Orion HCCA154 15" Dual 4 ohm Competition HCCA Series Car Subwoofer w/ a Hifonics MT Olympus Hercules 4K 4,000w Mono Amplifier Competition Car Audio Amp. A.) Will i need to upgrade my car's alternator or can i get away with just installing a capacitor? Second Q: Would I be better off purchasing the ORION HCCA152 15" 4000 Watt Dual 2 Ohm Voice Coil Subwoofer HCCA-152 to go with that AMPLIFIER or will it even make a difference? Your expertise is greatly appreciated. Thank you.

Posted on 6/14/2015 8:31:38 PM

Buck Pomerantz from Crutchfield

Daniel, Wiring the DVC 2-ohm subwoofer like this diagram will get 2000 watts RMS out of the amp. Wiring the DVC 4-ohm model like this will get 1600 watts RMS. Which do you like better: 1600 or 2000? As for the car's alternator, I'd say you'll probably need an upgrade - the amp will occasionally try to get up to 196 amperes from the system. Adding a capacitor alone will do very little to improve your electrical system's capacity.

Posted on 6/15/2015 2:45:55 PM

Tyler

I have 2 10" Rockford P2 and 2 12" Rockford P2. The 2 10" are powered by a Rockford r-1000 and the 2 12" are powered by a Rockford r-1200. The 4 subwoofers are in one enclosure, but each subwoofer has its own compartment to where it is sealed off from the other subwoofers so it doesn't ruin them. They are wired correctly and to the correct ohm stability of each amp. Also, all connections are fine as well. My question is concerning that when they are turned up to a certain volume, they will shut off and come right back on when I turn the volume down a little. I know this is because they aren't getting enough volts for that certain note of sound. I am wondering what you suggest to get to prevent this from happening. Sometimes they will shut off when they are not even displacing close to what I know they are capable of. All connections are fine, and both amps have power to them. My power wire is 0 gauge going into a distribution block with 4 gauge going to each amp. I am wondering if you suggest getting a capacitor or the big 3 package? I have thought about ordering both, but didn't know exactly what I need. I am trying to avoid buying a high output alternator because they are so expensive. I really don't care if I can turn the volume up all the way because it can damage the subwoofers, your ears, etc. I am just wondering if either the capacitor, big 3 upgrade, or both would help.

Posted on 6/17/2015 7:40:10 PM

Buck Pomerantz from Crutchfield

Tyler, Do your headlights dim when the music plays loud? Or are your amplifiers going into protection mode without any light-dimming? Amplifiers go into protection mode for a number of reasons. Insufficient current flow due to a loose ground. Low voltage because of a weak battery. Trying to drive a load below its minimum impedance. Overheating due to being driven too loudly (gain set improperly). So, start by having your battery checked. Then ensure the ground connection is clean and tight. Reset the amp gains. Check the wiring to see if the amps are really driving loads they can handle. Only after all that checks out okay should you move on to the choices of putting in a second battery, doing the big three, or adding a capacitor.

Posted on 6/18/2015 11:37:36 AM

justin bresnahan from United States

Do you leave the stock wire in place after doing the big 3 upgrade?

Posted on 6/24/2015 8:44:20 AM

Buck Pomerantz from Crutchfield

Justin, Yes, that is always a good thing to do.

Posted on 6/24/2015 10:30:15 AM

Jason from Salt lake city, UT

I have 2 jl w7 12 inch with a rockford fosgate amp t2500 and I have 4 15 kicker l7 2 ohms with a zx.11 2500
I do have a stock alternator . I have 2 batteries and one capacitor. My truck struggles to turn on at time I know my amps are using to much power out of the batteries. My question is what should I upgraded first? My battery or alternator. And what are some of the best brands out there ?

Posted on 7/5/2015 3:59:59 AM

Buck Pomerantz from Crutchfield

Jason, So you're powering your subwoofers with about 4500 watts RMS - that's an enormous draw on any vehicle's electrical system. Do you have an amp for your full-range speakers also? I'm not sure there's any stock system that could support this. Make sure each of those sub amps has its own 1/0-gauge power wire to the battery. Make sure your two batteries are up-to-date and keep their charge. After that, I can only see upgrading your alternator as the solution. You'll have to go to an automobile shop for a recommendation on high-current alternators.

Posted on 7/6/2015 4:53:39 PM

joey

i have a soundstream goliath 6500 4 mtx 75 12 inch woofers a autotek 1200 watt amp n a power acoustic 2500 watt amp the autotek is running 2 american bass 6.5 n a two rockford f tweets the power acoustic is running 4 6.5 mtx n 2 horns i have a optima yellow top battery under hood and a optima blue top marine batrry in trunk stereo plays for a amount of time then the 6 speakers in front cut off and eventuly the subs and the highs in back just play i have a 150 amp altenator and all power and groind wires are 0 gauge would u suggest uppong the amps on alt or another optims marine or both system is in a 73 impala

Posted on 7/12/2015 9:46:20 PM

Nolan from Arizona

I will be getting one Fi audio bl12" sub along with a CT sounds 1400.1 amplifier. I will be pushing 1500 watts rms. Anyways I drive a Honda Civic coupe 1.7L with a stock alternator and battery. I have already spent more money than I have and I'm trying to do this part as cheap as I can until I can do it right. I have a friend that is telling me I can get away with just buying a battery and a capacitor. But from all of the reading I've done, it seems like every single person has different opinions on it. If I don't upgrade my alternator and I just get the battery with a capacitor will the battery eventually die? What do you suggest I do?

Posted on 7/13/2015 12:22:56 PM

Buck Pomerantz from Crutchfield

Joey, If I understand, you have up to 2900 watts RMS going to subs, 150W going to two sets of speakers and 100W going to four more, for a total of 3600 watts RMS. At full power this system would need 522 amps of current. Even if we took into account a duty cycle for music of one-third, that would still mean you'd need 174 amps to run the audio system. Add in what it takes to run your car and you can see that a much larger (and expensive) alternator is called for in your situation.

Posted on 7/14/2015 11:23:58 AM

Buck Pomerantz from Crutchfield

Nolan, I suggest you wait until after your amplifier and subwoofer are installed, and after you start experiencing headlight dimming before you do any electrical system upgrade. There's no point in preparing to fix something that may not be broken.

Posted on 7/14/2015 12:09:56 PM

Michael from Ocala

I have (2) 12's DB 2000 4ohms 2000 watts , krank it up fc-1200 battery for the amp and a OE mopar battery for the 2013 jeep grand cherokee laredo, amp (clif design CDX20A 3k to 4k watts)
The 12 are dual coil and they were wired in series negative to negative and positive to positive
Getting light dimming. it has been over a year since I used the krank it up battery for audio..
1.) do you think the battery is bad or 2). should I be adding a 10 farad cap.. or would adding another battery by sufficient 3.) or checking the the ground

Posted on 7/15/2015 9:26:04 AM

Buck Pomerantz from Crutchfield

Michael, The only way to find out if your battery is bad or not is to take it to a battery or auto parts store and have them test it. Making sure your batteries are good and the ground wiring secure are the first steps in eliminating light dimming. If you've already added a second battery and are still having dimming issues, perhaps a capacitor will help. But it sounds like, for the long term, you're going to need a higher output alternator.

Posted on 7/15/2015 11:58:01 AM

juancho from nashua nh

quick question how would i wire 2 Alpine SWS-12D4 12" Dual-Voice-Coil 4-Ohm Subwoofer to a Rockford Fosgate PRIME R1000-1D its a Single-Channel Monoblock

Hi. I just bought a new car system. And as it seems, you guys really know your stuff. So I would just like to know if I need a bigger kondensator, and if I really need to do The Big 3. Just whatever I need. With the lowest cost possible, but still get full effeciency from the car sound system, and not screw the electrical stuff up.
What I got:
Subwoofer 4000 watt (2400 max output).
2x amplifiers 4000 watt each.
1x amplifier 10.000 watt
6x car speakers 1000 watt each.
1x kondensator 2 farad.
I think I must get a 4 farad kondensator?
I was thinking of using the 10.000 amplifier and 1 amplifier 4000 watt.
What do you guys think about this?

Posted on 7/21/2015 7:37:34 AM

Buck Pomerantz from Crutchfield

Signar, First of all, I suspect those huge power ratings you quote are peak or maximum specifications, which are useless for planning out a sound system. Use RMS ratings only. Secondly, it sounds like you haven't installed this gear yet. I suggest you wait until after it's installed in your vehicle and after you start experiencing headlight dimming before you do any electrical system upgrades. There's no point in preparing to fix something that may not be broken. You may not even need a capacitor (kondensator) at all.

Posted on 7/21/2015 3:22:38 PM

alex zakharov from United States

Ok...so i have a 2006 Hyundai Tucson. and got a hold of 2 12" sony explod woofers with a sony explod 1200 watt amp. everything was going great. until after about a year or so of blasting..the amp fried...(it was old ish). After that i got a Planet Audio 2400 watt 4 channel amp. and hooked it up to the woofers and it sounds amazing...but after short 4 months or so of blasting..my alternator fried. so i got a new alternator installed..and before i hook up the woofers again, i wanted to ask what would be the best solution for my case...i still dont know much about woofers. as much as i want power...i want my alternator to have as least strain as possible. please help

Posted on 7/29/2015 1:13:49 AM

Buck Pomerantz from Crutchfield

Alex, You didn't mention experiencing any headlight dimming when the music played before your alternator died, so maybe the amp had nothing to do with it failing. Did you ask your auto repairman what he thinks caused the alternator to fail? It was a 9-10 year old part. If after reconnecting your system you get light-dimming, then you'll know you need an electrical upgrade.

Posted on 7/29/2015 3:53:11 PM

Thomas rossiter from Oak forest

I have a 2009 Malibu that had a Bose system in and I got a jl 2 channel amp for a pair of jl audio 13 subwoffers and jl inside speakers with separate tweeters and a 400 watt amp hooked up to them hooked up to a clarion head unit with DVD and gps! My head lights dim when turned up loud to bass beat and amp sometimes shuts down and I'm getting crakling sounds from tweeters even when radio is off! 4 gauge wired was used and installed from qualifying installors! What do you think Is wrong?

Posted on 7/30/2015 9:22:22 PM

Buck Pomerantz from Crutchfield

Thomas, I think you should take your car back to your installer as soon as possible and politely point out the issues and give him a chance to correct any problems or suggest possible solutions.

Free tech support for the lifetime of your product

I had to call for support on the evening of installation. Your tech helped me get going in minutes. It was good to be able to call at that hour, and nice to talk to someone who knew the problem immediately.

David, Customer

We want you to enjoy the items you purchase from Crutchfield

If you're not satisfied with your purchase, you may return items that are complete and like new for any reason within 60 days